International Award for Human Genome Project

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

The Thai royal family awarded its annual prizes in Bangkok, Thailand, in late January 2018 in recognition of advances in public health and medicine – through the Prince Mahidol Award Foundation under the Royal Patronage. This foundation was established in 1992 to honor the late Prince Mahidol of Songkla, the Royal Father of His Majesty King Bhumibol Adulyadej of Thailand and the Royal Grandfather of the present King. Prince Mahidol is celebrated worldwide as the father of modern medicine and public health in Thailand.

The Human Genome Project has been awarded the 2017 Prince Mahidol Award for revolutionary advances in the field of medicine. The Human Genome Project was completed in 2003. It was an international, collaborative research program aimed at the complete mapping and sequencing of the human genome. Its final goal was to provide researchers with fundamental information about the human genome and powerful tools for understanding the genetic factors in human disease, paving the way for new strategies for disease diagnosis, treatment and prevention.

The resulting human genome sequence has provided a foundation on which researchers and clinicians now tackle increasingly complex problems, transforming the study of human biology and disease. Particularly it is satisfying that it has given the researchers the ability to begin using genomics to improve approaches for diagnosing and treating human disease thereby beginning the era of genomic medicine.

National Human Genome Research Institute (NHGRI) is devoted to advancing health through genome research. The institute led National Institutes of Health’s (NIH’s) contribution to the Human Genome Project, which was successfully completed in 2003 ahead of schedule and under budget. NIH, is USA’s national medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases.

Building on the foundation laid by the sequencing of the human genome, NHGRI’s work now encompasses a broad range of research aimed at expanding understanding of human biology and improving human health. In addition, a critical part of NHGRI’s mission continues to be the study of the ethical, legal and social implications of genome research.

NEW YORK (GenomeWeb) – Researchers at the University of Texas MD Anderson Cancer Center have developed a new breast cancer staging system that incorporates tumor biology as a critical prognostic indicator for women who undergo neoadjuvant therapy.

Published this week in JAMA Oncology, the Neo-Bioscore staging system incorporates HER2/ERBB2 status, which allows for more precise prognostic stratification of all breast cancer subtypes.

To date, breast cancer patient staging involved considering the size of the primary tumor, metastasis, or disease in the lymph nodes at the time of presentation as the primary factors.However, this fails to take into account the biology of the tumor, which has shown to be critically important, Elizabeth Mittendorf, associate professor of Breast Surgical Oncology at MD Anderson and corresponding author on the study, said in a statement.

The new system builds on the development of an earlier breast cancer staging system developed by MD Anderson, CPS+EG, that incorporates preclinical stage, estrogen receptor status, grade, and post-treatment pathologic stage. While it was an improvement from previous methods, it is no longer a sufficient staging system because it predates the routine use of trastuzumab in the neoadjuvant setting and therefore had a limited ability to provide prognostic information for HER2/ERBB2-positive patients, Mittendorf said.

To develop the staging system, the researchers conducted a retrospective study that evaluated 2,377 MD Anderson breast cancer patients who all had non-metastatic invasive breast cancer and were treated with neoadjuvant chemotherapy.

Each patient’s clinicopathologic data were recorded, including age, clinical and pathological stage, ER status, HER2/ERBB2 status, and nuclear grade. Patients’ ER status was recorded as a percentage of cells staining positive under immunohistochemical analysis. Their ERBB2 status was defined as positive at a reading of 3+ on immunohistochemical analysis or when gene amplification was shown on fluorescence in situ hybridization.

All patients received an anthracycline and/or taxane-based neoadjuvant chemotherapy regimen. Patients with HER2/ERBB2-positive disease routinely completed one year of trastuzumab therapy. After completing chemotherapy, patients underwent either breast-conserving therapy or mastectomy with axillary evaluation with or without post-mastectomy irradiation.

Patients’ CPS+EG score was determined according to the previously published staging system and was calculated twice (once using 1 percent or higher as the cutoff for ER positivity and again using 10 percent or higher as the cutoff).

After the researchers determined a CPS+EG score for each patient, they added the patient’s respective HER2/ERBB2 status to the model. They then constructed the novel staging system by adding a point to the CPS+EG score for HER2-negative tumors. In the study cohort, 591 patients were HER2/ERBB2 positive.

The researchers found that in addition to validating previous findings that CPS+EG score improved prognostication of patients, the Neo-Bioscore created a more refined stratification in approximately 75 percent of the study cohort. This shift reflects the number of HER2/ERBB2-negative tumors in the study and demonstrated that adding HER2/ERBB2 standards created a highly significant improvement.

“With this tool, I can give my patients the precise information they are looking for: a more refined prognosis. Also, with this data, we will know which patients are in greatest need of additional therapy,” Mittendorf said. “Hopefully these findings will result in more informed conversations between doctor and patient.”

The Neo-Bioscore Update for Staging Breast Cancer Treated With Neoadjuvant ChemotherapyIncorporation of Prognostic Biologic Factors Into Staging After Treatment

Objective To validate the CPS+EG staging system using the new definition of ER positivity (≥1%) and to develop an updated staging system (Neo-Bioscore) that incorporates ERBB2 status into the previously developed CPS+EG.

Design, Setting, and Participants Retrospective review of data collected prospectively from January 2005 through December 2012 on patients with breast cancer treated with neoadjuvant chemotherapy at The University of Texas MD Anderson Cancer Center.

Main Outcomes and Measure Prognostic scores were computed using 2 versions of the CPS+EG staging system, one with ER considered positive if it measured 10% or higher, the other with ER considered positive if it measured 1% or higher. Fits of the Cox proportional hazards model for the 2 sets of prognostic scores were compared using the Akaike Information Criterion (AIC). Status of ERBB2 was added to the model, and the likelihood ratio test was used to determine improvement in fit.

Results A total of 2377 patients were included; all were women (median age, 50 years [range, 21-87 years]); ER status was less than 1% in 28.9%, 1% to 9% in 8.3%, and 10% or higher in 62.8%; 591 patients were ERBB2 positive. Median follow-up was 4.2 years (range, 0.5-11.7 years). Five-year disease-specific survival was 89% (95% CI, 87%-90%). Using 1% or higher as the cutoff for ER positivity, 5-year disease-specific survival estimates determined using the CPS+EG stage ranged from 52% to 98%, thereby validating our previous finding that the CPS+EG score facilitates more refined categorization into prognostic subgroups than clinical or final pathologic stage alone. The AIC value for this model was 3333.06, while for a model using 10% or higher as the cutoff for ER positivity, it was 3333.38, indicating that the model fits were nearly identical. The improvement in fit of the model when ERBB2 status was added was highly significant, with 5-year disease-specific survival estimates ranging from 48% to 99% (P < .001). Incorporating ERBB2 into the staging system defined the Neo-Bioscore, which provided improved stratification of patients with respect to prognosis.

Conclusions and Relevance The Neo-Bioscore improves our previously validated staging system and allows its application in ERBB2-positive patients. We recommend that treatment response and biologic markers be incorporated into the American Joint Committee on Cancer staging system.

A team of investigators from Houston Methodist Research Institute may have transformed the treatment of metastatic triple negative breast cancer by creating the first drug to successfully eliminate lung metastases in mice.

The majority of cancer deaths are due to metastases to the lung and liver, yet there is no cure. Existing cancer drugs provide limited benefit due to their inability to overcome biological barriers in the body and reach the cancer cells in sufficient concentrations. Houston Methodist nanotechnology and cancer researchers have solved this problem by developing a drug that generates nanoparticles inside the lung metastases in mice.

In this study, 50 percent of the mice treated with the drug had no trace of metastatic disease after eight months. That’s equivalent to about 24 years of long-term survival following metastatic disease for humans.

Due to the body’s own defense mechanisms, most cancer drugs are absorbed into healthy tissue causing negative side effects, and only a fraction of the administered drug actually reaches the tumor, making it less effective, said Mauro Ferrari, Ph.D, president and CEO of the Houston Methodist Research Institute. This new treatment strategy enables sequential passage of the biological barriers to transport the killing agent into the heart of the cancer. The active drug is only released inside the nucleus of the metastatic disease cell, avoiding the multidrug resistance mechanism of the cancer cells. This strategy effectively kills the tumor and provides significant therapeutic benefit in all mice, including long-term survival in half of the animals.

This finding comes 20 years after Ferrari started his work in nanomedicine. Ferrari and Haifa Shen, M.D., Ph.D., are co-senior authors on the paper, which describes the action of the injectable nanoparticle generator (iNPG), and how a complex method of transporting a nano-version of a standard chemotherapy drug led to never before seen results in mice models with triple negative breast cancer that had metastasized to the lungs.

“This may sound like science fiction, like we’ve penetrated and destroyed the Death Star, but what we discovered is transformational. We invented a method that actually makes the nanoparticles inside the cancer and releases the drug particles at the site of the cellular nucleus. With this injectable nanoparticle generator, we were able to do what standard chemotherapy drugs, vaccines, radiation, and other nanoparticles have all failed to do,” said Ferrari.

Houston Methodist has developed good manufacturing practices (GMP) for this drug and plans to fast-track the research to obtain FDA-approval and begin safety and efficacy studies in humans in 2017.

“I would never want to overpromise to the thousands of cancer patients looking for a cure, but the data is astounding,” said Ferrari, senior associate dean and professor of medicine, Weill Cornell Medicine. “We’re talking about changing the landscape of curing metastatic disease, so it’s no longer a death sentence.”

The Houston Methodist team used doxorubicin, a cancer therapeutic that has been used for decades but has adverse side effects to the heart and is not an effective treatment against metastatic disease. In this study, doxorubicin was packaged within the injectable nanoparticle generator that is made up of many components.

Shen, a senior member of the department of nanomedicine at Houston Methodist Research Institute, explains that each component has a specific and essential role in the drug delivery process. The first component is the nanoporous silicon material that naturally degrades in the body. The second component is a polymer made up of multiple strands that contain doxorubicin. Once inside the tumor, the silicon material degrades, releasing the strands. Due to natural thermodynamic forces, these strands curl-up to form nanoparticles that are taken up by the cancer cells. Once inside the cancer cells, the acidic pH close to the nucleus causes the drug to be released from the nanoparticles. Inside the nucleus, the active drug acts to kill the cell.

“If this research bears out in humans and we see even a fraction of this survival time, we are still talking about dramatically extending life for many years. That’s essentially providing a cure in a patient population that is now being told there is none,” said Ferrari, who holds the Ernest Cockrell Jr. Presidential Distinguished Chair and is considered one of the founders of nanomedicine and oncophysics (physics of mass transport within a cancer lesion).

The Houston Methodist team is hopeful that this new drug could help cancer physicians cure lung metastases from other origins, and possibly primary lung cancers as well.

Cutaneous melanoma is a type of skin cancer that originates in melanocytes, the cells that are producing melanin. While being the least common type of skin cancer, melanoma is the most aggressive one with invasive characteristics and accounts for the majority of death incidences among skin cancers. Melanoma has an annual rate of 160,000 new cases and 48,000 deaths worldwide. Melanoma affects mainly Caucasians exposed to sun high UV irradiation. Among the genetic factors that characterize the disease, BRAF mutation (V600E) is found in most cases of melanoma (80%). Awareness toward risk factors of melanoma should lead to prevention and early detection*. There are several developmental stages (I-IV) of the disease, starting from local non-invasive melanoma, through invasive and high risk melanoma, up to metastatic melanoma. As with other cancers, the earlier stage melanoma is being detected, the better odds for full recovery are. Treatment is usually involving surgery to remove the local tumor and its margins, and when necessary also to remove the proximal lymph node(s) that drain the tumor. In high stages melanoma, adjuvant therapy is given in the form of chemotherapy (Dacarbazine and Temozolomide) and immunotherapy (IL-2 and IFN). Until recently no useful treatment was available for metastatic melanoma. However, research efforts had led to the development of two new drugs against metastatic melanoma: Vemurafenib (Zelboraf), a B-Raf inhibitor; and Ipilimumab (Yervoy), a monoclonal antibody that blocks the inhibitory signal of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). Both drugs are now available for clinical use presenting good results.

Personalized therapy for melanoma

In an attempt to develop personalized therapies for malignant melanoma, a unique strategy has been taken by the group of Prof. Yardena Samuels at the NIH (now situated at the WIS) to identify recurring genetic alterations of metastatic cutaneous melanoma. The researchers approach employed the collections of hundreds of tumors samples taken from metastasized melanoma patients together with matched normal blood tissues samples. The samples are undergoing exome sequencing for the analysis of somatic mutations (namely mutations that evolved during the progress of the disease to the stage of metastatic melanoma, unlike genomic mutations that may have contribute to the formation of the disease). The discrimination of such tumor related somatic mutations is done by comparison to the exome sequencing of the patient’s matched blood cells DNA. In addition, the malignant cells derived from the removed cancer tissue of each patient are extracted to form a cell line and are grown in culture. These cells are easily cultivate in culture with no special media supplements, nor further genetic manipulations such as hTERT are needed, and are extremely aggressive as determined by various cell culture and in vivo tests. The ability to grow these primary tumor-derived cell lines in culture has a great value as a tool for studying and characterizing the biochemical, functional, and clinical aspects of the mutated genes identified.

In one study [1] Samuels and her colleagues performed this sequencing process for mutation analysis for the protein tyrosine kinase (PTK) gene family, as PTKs are frequently mutated in cancer. Using high-throughput gene sequencing to analyze the entire PTK gene family, the researchers have identified 30 somatic mutations affecting the kinase domains of 19 PTKs and subsequently evaluated the entire coding regions of the genes encoding these 19 PTKs for somatic mutations in 79 melanoma samples. The most frequent mutations were found in ERBB4, a member of the EGFR/ErbB family of receptor tyrosine kinase (RTK), were 19% of melanoma patients had such mutations. Seven missense mutations in the ERBB4 gene were found to induce increased kinase activity and transformation capability. Melanoma derived cell lines that were expressing these mutant ERBB4 forms had reduced cell growth after silencing ERBB4 by RNAi or after treatment with the ERBB inhibitor Lapatinib. Lapatinib is already in use in the clinic for the treatment of HER2 (ErbB2) positive breast cancers patients. Following this study, a clinical trial is now conducted with this drug to evaluate its effect in cutaneous metastatic melanoma patients harboring mutations in ERBB4.

In another study of this group [2], the scientists employed the exome sequencing method to analyze the somatic mutations of 734 G protein coupled receptors (GPCRs) in melanoma. GPCRs are regulating various signaling pathways including those that affect cell growth and play also important role in human diseases. This screen revealed that GRM3 gene that encode the metabotropic glutamate receptor 3 (mGluR3), was frequently mutated and that one of its mutations clustered within one position. Mutant GRM3 was found to selectively regulate the phosphorylation of MEK1 leading to increased anchorage-independent cell growth and cellular migration. Tumor derived melanoma cells expressing mutant GRM3 exhibited reduced cell growth and migration upon knockdown of GRM3 by RNAi or by treatment with the selective MEK inhibitor, Selumetinib (AZD-6244), a drug that is being testing in clinical trials. Altogether, the results of this study point to the increased violent characteristics of melanomas bearing mutational GRM3.

In a third study, melanoma samples were examined for somatic mutations in 19 human genes that encode ADAMTS proteins [3]. Some of the ADAMTS genes have been suggested before to have implication in tumorigenesis. ADAMTS18, which was previously found to be a candidate cancer gene, was found in this study to be highly mutated in melanoma. ADAMTS18 mutations were biologically examined and were found to induce an increased proliferation of melanoma cells, as well as increased cell migration and metastasis. Moreover, melanoma cells expressing these mutated ADAMTS18 had reduced cell migration after RNAi-mediated knockdown of ADAMTS18. Thus, these results suggest that genetic alteration of ADAMTS18 plays a major role in melanoma tumorigenesis. Since ADAMTS genes encode extracellular proteins, their accessibility to systematically delivered drugs makes them excellent therapeutic targets.

Conclusive remarks

The above illustrated research approach intends to discover frequent melanoma-specific mutations by employing high-throughput whole exome and genome sequencing means. For the most highly mutated genes identified, the biochemical, functional, and clinical aspects are being characterized to examine their relevancy to the disease outcomes. This approach therefore introduces new opportunities for clinical intervention for the treatment of cutaneous melanoma. In addition to the discovery of novel highly mutated genes, this approach may also help determine which pathways are altered in melanoma and how these genes and pathways interact. Finding melanoma-associated highly mutated genes could lead to personalized therapeutics specifically targeting these altered genes in individual melanomas. Along with the opportunity to develop new agents to treat melanoma, the approach takes advantage of existing anti-cancer drugs, utilizing them to treat these mutated genes melanoma individuals. In addition to their potential for therapeutics, the discovery of highly mutated genes in melanoma patients may lead to the discovery of new markers that may assist the diagnosis of the disease. The implications of these screenings findings on other types of cancer bearing common pathways similar to melanoma should be examined as well. Finally, this elegant approach should be adopted in research efforts of other cancer types.

Annual treatment costs for musculoskeletal diseases in the US are roughly 7.7% (~ $849 billion) of total gross domestic product. Such disorders are the main cause of physical disability in US. Almost half of all chronic conditions in people can be attributed to bone and joint disorders. In addition there is increasing ageing population and associated increases in osteoporosis and other diseases, rising incidences of degenerative intervertebral disk diseases and numbers of revision orthopedic arthroplasty surgeries, and increases in spinal fusions. All these factors contribute towards the increasing requirement of bone regeneration and reconstruction methods and products. Delivery of therapeutic grade products to bone has various challenges. Parenteral administration limits the efficient delivery of drugs to the required site of injury and local delivery methods are often expensive and invasive. The theme issue of Advance Drug Delivery reviews focuses on the current status of drug delivery to bone and the issues facing this field. Here is the first part of these reviews and research articles.

Abstract

Demineralized bone matrix (DBM) is an osteoconductive and osteoinductive commercial biomaterial and approved medical device used in bone defects with a long track record of clinical use in diverse forms. True to its name and as an acid-extracted organic matrix from human bone sources, DBM retains much of the proteinaceous components native to bone, with small amounts of calcium-based solids, inorganic phosphates and some trace cell debris. Many of DBM’s proteinaceous components (e.g., growth factors) are known to be potent osteogenic agents. Commercially sourced as putty, paste, sheets and flexible pieces, DBM provides a degradable matrix facilitating endogenous release of these compounds to the bone wound sites where it is surgically placed to fill bone defects, inducing new bone formation and accelerating healing. Given DBM’s long clinical track record and commercial accessibility in standard forms and sources, opportunities to further develop and validate DBM as a versatile bone biomaterial in orthopedic repair and regenerative medicine contexts are attractive.

The regeneration of large bone defects caused by trauma or disease remains a significant clinical problem. Although osteoinductive growth factors such as bone morphogenetic proteins have entered clinics, transplantation of autologous bone remains the gold standard to treat bone defects. The effective treatment of bone defects by protein therapeutics in humans requires quantities that exceed the physiological doses by several orders of magnitude. This not only results in very high treatment costs but also bears considerable risks for adverse side effects. These issues have motivated the development of biomaterials technologies allowing to better control biomolecule delivery from the solid phase. Here we review recent approaches to immobilize biomolecules by affinity binding or by covalent grafting to biomaterial matrices. We focus on biomaterials concepts that are inspired by extracellular matrix (ECM) biology and in particular the dynamic interaction of growth factors with the ECM. We highlight the value of synthetic, ECM-mimicking matrices for future technologies to study bone biology and develop the next generation of ‘smart’ implants.

Abstract

Calcium phosphate cements are used as synthetic bone grafts, with several advantages, such as their osteoconductivity and injectability. Moreover, their low-temperature setting reaction and intrinsic porosity allow for the incorporation of drugs and active principles in the material. It is the aim of the present work to: a) provide an overview of the different approaches taken in the application of calcium phosphate cements for drug delivery in the skeletal system, and b) identify the most significant achievements. The drugs or active principles associated to calcium phosphate cements are classified in three groups, i) low molecular weight drugs; ii) high molecular weight biomolecules; and iii) ions.

Abstract

Silk fibroin (SF) is a biopolymer with distinguishing features from many other bio- as well as synthetic polymers. From a biomechanical and drug delivery perspective, SF combines remarkable versatility for scaffolding (solid implants, hydrogels, threads, solutions), with advanced mechanical properties and good stabilization and controlled delivery of entrapped protein and small molecule drugs, respectively. It is this combination of mechanical and pharmaceutical features which renders SF so exciting for biomedical applications. This pattern along with the versatility of this biopolymer has been translated into progress for musculoskeletal applications. We review the use and potential of silk fibroin for systemic and localized delivery of therapeutics in diseases affecting the musculoskeletal system. We also present future directions for this biopolymer as well as the necessary research and development steps for their achievement.

As a unique human bone extract approved for implant use, demineralized bone matrix (DBM) retains substantial amounts of endogenous osteoconductive and osteoinductive proteins. Commercial preparations of DBM represent a clinically accessible, familiar, widely used and degradable bone-filling device, available in composite solid, strip/piece, and semi-solid paste forms. Surgically placed and/or injected, DBM releases its constituent compounds to bone sites with some evidence for inducing new bone formation and accelerating healing. Significantly, DBM also has preclinical history as a drug carrier by direct loading and delivery of several important classes of therapeutics. Exogenous bioactive agents, including small molecule drugs, protein and peptide drugs, nucleic acid drugs and transgenes and therapeutic cells have been formulated within DBM and released to bone sites to enhance DBM’s intrinsic biological activity. Local release of these agents from DBM directly to surgical sites in bone provides improved control of dosing and targeting of both endogenous and exogenous bioactivity in the context of bone healing using a clinically familiar product. Given DBM’s long clinical track record and commercial accessibility in standard forms and sources, opportunities to formulate DBM as a versatile matrix to deliver therapeutic agents locally to bone sites in orthopedic repair and regenerative medicine contexts are attractive.

Abstract

Biodegradable nanofibers are important scaffolding materials for bone regeneration. In this paper, the basic concepts and recent advances of self-assembly, electrospinning and thermally induced phase separation techniques that are widely used to generate nanofibrous scaffolds are reviewed. In addition, surface functionalization and bioactive factor delivery within these nanofibrous scaffolds to enhance bone regeneration are also discussed. Moreover, recent progresses in applying these nanofiber-based scaffolds to deliver stem cells for bone regeneration are presented. Along with the significant advances, challenges and obstacles in the field as well as the future perspective are discussed.

Bone is one of the few tissues in the human body with high endogenous healing capacity. However, failure of the healing process presents a significant clinical challenge; it is a tremendous burden for the individual and has related health and economic consequences. To overcome such healing deficits, various concepts for a local drug delivery to bone have been developed during the last decades. However, in many cases these concepts do not meet the specific requirements of either surgeons who must use these strategies or individual patients who might benefit from them. We describe currently available methods for local drug delivery and their limitations in therapy. Various solutions for drug delivery to bone focusing on clinical applications and intra-operative constraints are discussed and drug delivery by implant coating is highlighted. Finally, a new set of design and performance requirements for intra-operatively customized implant coatings for controlled drug delivery is proposed. In the future, these requirements may improve approaches for local and intra-operative treatment of patients.

Current state of the art reconstruction of bony defects in the craniomaxillofacial (CMF) area involves transplantation of autogenous or allogenous bone grafts. However, the inherent drawbacks of this approach strongly urge clinicians and researchers to explore alternative treatment options. Currently, a wide interest exists in local delivery of biomolecules from synthetic biomaterials for CMF bone regeneration, in which small biomolecules are rapidly emerging in recent years as an interesting adjunct for upgrading the clinical treatment of CMF bone regeneration under compromised healing conditions. This review highlights recent advances in the local delivery small and large biomolecules for the clinical treatment of CMF bone defects. Further, it provides a perspective on the efficacy of biomolecule delivery in CMF bone regeneration by reviewing presently available reports of pre-clinical studies using various animal models.

Abstract

Many surgical procedures require the placement of an inert or tissue-derived implant deep within the body cavity. While the majority of these implants do not become colonized by bacteria, a small percentage develops a biofilm layer that harbors invasive microorganisms. In orthopaedic surgery, unresolved periprosthetic infections can lead to implant loosening, arthrodeses, amputations and sometimes death. The focus of this review is to describe development of an implant in which an antibiotic tethered to the metal surface is used to prevent bacterial colonization and biofilm formation. Building on well-established chemical syntheses, studies show that antibiotics can be linked to titanium through a self-assembled monolayer of siloxy amines. The stable metal–antibiotic construct resists bacterial colonization and biofilm formation while remaining amenable to osteoblastic cell adhesion and maturation. In an animal model, the antibiotic modified implant resists challenges by bacteria that are commonly present in periprosthetic infections. While the long-term efficacy and stability is still to be established, ongoing studies support the view that this novel type of bioactive surface has a real potential to mitigate or prevent the devastating consequences of orthopaedic infection.

Abstract

Non-invasive treatment of injuries and disorders affecting bone and connective tissue remains a significant challenge facing the medical community. A treatment route that has recently been proposed is nitric oxide (NO) therapy. Nitric oxide plays several important roles in physiology with many conditions lacking adequate levels of NO. As NO is a radical, localized delivery via NO donors is essential to promoting biological activity. Herein, we review current literature related to therapeutic NO delivery in the treatment of bone, skin and tendon repair.

Genome-scale studies of cancer samples have begun to provide a global depiction of genetic alterations in human cancers, but the complexity and volume of data that emerge from these efforts have made dissecting the underlying biology of cancer difficult, and little is known about the functions of most of the candidates that emerge. For example, in studies of 489 primary high-grade serous ovarian cancer genomes, 1825 genes were identified as targeted by recurrent amplification events. Systematic approaches to study the function of genes in cancer cell lines, such as genome-scale pooled short hairpin RNA (shRNA) screens, offer a means to assess the consequences of the genetic alterations found in such genome characterization efforts. The comprehensive characterization of a large number of cancer genomes will eventually lead to a compendium of genetic alterations in specific cancers. Unfortunately, the number and complexity of identified alterations complicate endeavors to identify biologically relevant mutations critical for tumor maintenance because many of these targets are not amenable to manipulation by small molecules or antibodies. RNA interference provides a direct way to study putative cancer targets; however, specific delivery of therapeutics to the tumor parenchyma remains an intractable problem.

Recently an shRNA-based approach was used to find genes that are both overexpressed in human primary tumors and essential for the proliferation of ovarian cancer cells. This approach identified 54 overexpressed and essential genes in ovarian cancer and 16 genes in non–small cell lung cancer that required further validation in vivo. Furthermore, many of these candidates represent targets that are not amenable to antibody-based therapeutics or traditional small molecule approaches. Thus, if one envisions a discovery pipeline that begins with cancer genomes and ends with novel therapeutics, there is a bottleneck at the point of in vivo validation of novel targets. Achieving silencing in the epithelial cells in the tumor parenchyma is especially critical to study the genetic alterations of interest. RNA interference (RNAi) is a potentially attractive means to silence the expression of candidate genes in vivo, particularly for undruggable gene products. However, systemic delivery of small interfering RNA (siRNA) to tumors has been challenging, owing to rapid clearance, susceptibility to serum nucleases, and endosomal entrapment of small RNAs, in addition to their inherent inadequate tumor penetration. Tumor penetration is also a problem for the delivery of siRNA and shRNA, among other cargos, and is characterized by limited transport into the extravascular tumor tissue beyond the perivascular region. This low penetration is thought to arise from the combination of dysfunctional blood vessels that are poorly perfused and a high interstitial pressure, especially in solid tumors, in part due to dysfunctional lymphatics. The leakiness of tumor vessels partially counteracts the poor penetration [the so-called enhanced permeability and retention (EPR) effect], but the size dependence and variability of this property can limit its usefulness. Desmoplastic stromal barriers can further impede transport of therapeutics through tumors. A new class of tumor-penetrating peptides has been described recently, which home to several types of tumors and leverage a consensus R/KXXR/K C-terminal peptide motif [the C-end rule (CendR)] to stimulate transvascular transport and rapidly deliver therapeutic cargo deep into the tumor parenchyma. These peptides are tumorspecific, unlike canonical cell-penetrating peptides (CPPs) that do not display cell- or tissue-type specificity, and are able to improve the delivery of small molecules, antibodies, and nanoparticles. Despite their promise, this class of peptides has not been successfully co-opted for siRNA delivery, in part owing to the additional challenges of delivering oligonucleotides across cell membranes, out of endosomes, and into the cytosol to achieve gene silencing. Here, an siRNA delivery vehicle has been designed that was tumorpenetrating and modular, so it could be easily assembled in a single step to accommodate different payloads to various genes of interest. It can be envisaged that such a technology would enable a platform wherein novel targets can be identified by structural and functional genomics and subsequently rapidly credentialed both in vitro and in vivo. Followup studies could then identify the mechanism of action underlying the observations and establish (and ultimately prioritize) novel oncogenes as therapeutic targets. To achieve this goal, a systematic effort was combined to identify genes that are both essential and genetically altered in human cancer cell lines and tumors with the development and deployment of a novel tumor-specific and tissue-penetrating siRNA delivery platform.

Current genome characterization efforts will eventually provide insight into the genetic alterations that occur in most cancers and may define new therapeutic targets. However, most epithelial cancers harbor hundreds of genetic alterations as a consequence of genomic instability. For example, whereas recurrent somatic alterations occur in a small number of genes in high-grade ovarian cancers, ovarian cancer genomes are characterized by multiple regions of copy number gain and loss involving at least 1825 genes. This genomic chaos complicates efforts to identify biologically relevant mutations critical for tumor maintenance.

To isolate which recurrent genetic alterations are involved in cancer initiation, tumor maintenance, and/or metastasis, functional assays can be performed after systematic manipulation of the candidate oncogenes. Results from Project Achilles was combined, a large scale screening effort to identify genes essential for proliferation and survival in human cancer cell lines with genome characterization of high-grade ovarian cancers. Using this approach, an oncogene candidate was identified, ID4, which was amplified in 32% of high-grade serous ovarian cancers. ID4 is overexpressed in a large fraction of high-grade serous ovarian cancers, and ovarian cancer cell lines that overexpress ID4 are highly dependent on ID4 for survival and tumorigenicity. Expression of ID4 at levels corresponding to those observed in patient-derived samples induced transformation of immortalized ovarian and FT epithelial cells.

In summary, a targeted TPN was developed capable of precisely delivering siRNA into the tumor parenchyma, and have combined this technology with large-scale methods to credential ID4 as an oncogene target in ovarian cancer. Because large-scale efforts to characterize all cancer genomes accelerate, this capability illustrates a path to identify genes that are altered in tumors, validate those that are critical to cancer initiation and maintenance, and rapidly evaluate in vivo the subset of such genes amenable to RNAi therapies and clinical translation. These observations not only credential ID4 as an oncogene in 32% of high-grade ovarian cancers but also provide a framework for the identification, validation, and understanding of potential therapeutic cancer targets.